The present invention relates to the presumptive identification of bacteria, and in particular to the presumptive identification the microorganisms Bacillus cereus and Bacillus thuringiensis.
Chapter 35 of the Compendium of Methods for the Microbiological Examination of Foods, American Public Health Association, 1992, questions whether Bacillus thuringiensis is a separate species or a variety of Bacillus cereus because of the cultural similarity of the microorganisms. Here they are considered separate species. Bacillus cereus and Bacillus thuringiensis are found on a variety of foods, and have been implicated in food poisoning of humans. For this reason and the fact that they are similar in characteristics, it is desirable to consider both in the process of making a presumptive identification from a mixed sample.
The Compendium of Methods for the Microbiological Examination of Foods, supra, describes the Kim-Goepfert agar and the mannitol yolk polymyxin agar for presumptive identification of Bacillus cereus from a mixed sample, and points out that these plating media are not 100% selective and may be difficult to interpret.
The paper entitled Phosphatidylinositol-Specific Phospholipases C from Bacillus cereus and Bacillus thuringiensis by O. H. Griffith, J. J. Volwerk and A. Kuppe, Methods in Enzymology, Vol. 197 Academic Press, Inc. 1991, investigates the production of the enzyme Phosphatidylinositol-Specific Phospholipases C produced by both Bacillus cereus and Bacillus thuringiensis. M. Ryan, J. Huang, O. H. Griffith, J. F. W. Keana, and J. J. Volwerk describe detection of Phosphatidylinositol-Specific Phospholipase C produced by Bacillus cereus and Bacillus thuringiensis with a chemiluminescent substrate in the paper entitled A Chemiluminescent Substrate for the Detection of Phosphatidylinositol-Specific Phospholipase C, Analytical Biochemistry, Vol. 214, pages 548-556 (1993). In a paper entitled Isolation and Detection of Listeria monocytogenes Using Fluorogenic and Chromogenic Substrates for Phosphatidylinositol-Specific Phospholipase C, by L. Restaino (the present inventor), E. W. Frampton, R. M. Irbe, Gunter Schabert, and Hans Spitz, Journal of Food Protection, Vol 62, No. 3, 1999, Pages 244-251, a chromogenic substrate is disclosed for Listeria responsive to the production of phosphatidylinositol-specific phospholipase C.